Analog phase error detectors of various types have been used in analog phase lock loops for many years. More recently, digital phase error detectors have come into use in digital phase lock loops. The latter have provided the advantages of repeatability and sealability often associated with digital hardware. Digital phase error detectors, however, also have a disadvantage in that they are subject to quantization error, which generates quantization noise in the phase lock loop signals.
Analog phase error detectors and analog phase lock loops are not subject to quantization error and thus do not generate quantization noise. Unfortunately, they lack the repeatability and sealability provided by digital phase error detectors and digital phase lock loops. Analog phase error detectors and analog phase lock loops generally have required precision component values, which have needed to be adjusted depending upon the frequency of operation.
Thus, what is needed is a phase error detector and a phase lock loop that can provide the advantages of both the analog and digital domains, without including the disadvantages of either domain. A phase error detector and a phase lock loop are needed that can provide the repeatability and scalability associated with the digital domain, with the freedom from quantization error and quantization noise associated with the analog domain.